Orientation and/or location tracking have long been important for navigation for shipping, aviation, and unmanned vehicles, manufacturing, warehouse operation, athletic training, physical therapy, animal tracking, computer games, and for such emerging fields as virtual reality and augmented reality. Schemes for measuring orientation and/or position of a moving object have been described in US patents and US patent applications, including U.S. Pat. No. 4,742,356 to Kuipers, U.S. Pat. No. 5,216,429 to Nakagawa, U.S. Pat. No. 5,744,953 to Hansen, U.S. Pat. No. 5,729,129 to Acher, U.S. Pat. No. 5,930,741 to Kramer, U.S. Pat. No. 6,011,526 to Toyoshima, 2003/0135327 to Levine, 2004/0006424 to Joyce, and 2005/0256675 to Kurata, all of which are incorporated herein by reference.
A paper, Correal N., Kyperountas S., Shi Q. and Welborn M., “An UWB Relative Location System” Proceedings of the IEEE Conference on UWB Systems and Technologies, 394-397 (2003), (“the Correal paper”), incorporated herein by reference, provides a review of RF location tracking methodologies, and is available at http://www.ee.vt.edu/˜ha/research/uwb/sensor_static_location/uwb_relative_location.pdf The Correal paper reports an RMS 2-D location error of only 0.16 feet with an RMS error of 0.1 and 0.12 feet in the x and y directions respectively.
Schemes have also been described in papers, all of which are incorporated herein by reference, including:    Werb J. and Lanzl C. “Designing a Positioning System for Finding Things and People indoors”, IEEE Spectrum, September 1998, vol. 35, no. 9, pp. 71-78.    Lee J-Y. and Scholtz R. “Ranging in a Dense Multipath Environment Using an UWB Radio Link”, Journal on Selected Areas in Communications, vol. 20, no. 9, pp. 1677-1683, December 2002;    Fontana R. “UWB Precision Asset Location System”, IEEE Conference on UWB Systems and Technologies, 2002;    R. Flemming and C. Kushner, “Low Power, Miniature, Distributed Position Location and Communication Devices Using Ultrawideband Nonsinusoidal Communication Technology,” Aetherwire Inc., Semi-Annual Tech. Rep., ARPA Contract J-FBI-94-058 July 1995;    Patwari N., Hero A., Perkins M., Correal N. and O'Dea B. “Relative Location Estimation in Wireless Sensor Networks,” IEEE Transactions on Signal Processing, Special Issue on Signal Processing in Networks, vol. 51, no. 8, August 2003, pp. 2137-2148;
Commercial wireless UWB ranging products are available from Multispectral Solutions, Inc. (Germantown, Md., USA), such as the Spider 650. This manufacturer claims “The Spider-650 is a lightweight, portable RADAR device which utilizes ultra wideband (UWB) short-pulse technology to determine the presence of, and the precise distance to, a target by measuring the roundtrip time-of-flight of the transmitted pulse to the target and back. Spider-650 can accurately determine the range to targets within a 50 foot distance from the unit, with a measurement accuracy of ±1 foot. Spider-650 provides a simple RS-232 or RS-485 interface for external control and monitoring.” http://www.multispectral.com/
Electronic sensors have been developed to measure angles between body segments and to measure range of motion of various joints, as described in commonly assigned U.S. patent application Ser. No. 08/990,912 to Arms, (“the '912 patent application”), filed on Dec. 15, 1997, and incorporated herein by reference. The '912 patent application describes a pair of housings that contain a pair of inclinometer board assemblies and the cable and plugs for their connection. The inclinometer board assemblies each include pairs of accelerometers oriented orthogonal to each other, a/d converters, a multiplexer, a voltage regulator, and a microprocessor. The microprocessor computes the angle of each inclinometer housing with respect to the other.
Commonly assigned U.S. patent application Ser. No. 09/457,493 to Arms, (“the '493 patent application”), filed on Dec. 8, 1999, and incorporated herein by reference discloses an inclinometer that includes three orthogonal accelerometers and three orthogonal magnetometers used to measure earth's gravitational and magnetic field vectors from which pitch, roll, and yaw (compass heading) are calculated. Low pass filters are provided to minimize effects due to inertial inputs to the accelerometers that might interfere with accuracy. The '493 application also provides a digital network to allow multiple devices to be wired together on a single bus, a feature useful for applications, such as posture monitoring.
Commonly assigned U.S. patent application Ser. No. 10/082,562 to Arms, (“the '562 patent application”), filed on Feb. 23, 2001, and incorporated herein by reference, describes a posture monitor that can distinguish lying down, sitting, and standing positions.
However, a better system for monitoring orientation and position has been needed that provides improved ability to obtain, process, and communicate such data, and this solution is provided by the following description.